Let G be a connected, simply-connected, simple algebraic group over C. We fix a Borel subgroup B of G and a maximal torus T ⊂ B. We denote their Lie algebras by g, b, h respectively. Let P+ ⊂ h be the set of dominant integral weights. For any λ ∈ P+, let V (λ) be the finite dimensional irreducible g-module with highest weight λ. We fix a positive integer l and let Rl(g) be the free Z-module wit...